Numerous items are packaged in sealed containers including products such as beverages, foodstuffs, nutritional products, medical products and generally any other items wherein it is desirable to keep the same from becoming spoiled or contaminated for a period of time. Various products are sterilized or heat treated after being sealed in a container such as by utilizing a retorting process in which the container that contains the food products is heated to relatively high temperatures such as in a range from about 121° C. to 132° C. or above. The containers can also be subjected to external pressurization during retorting to counteract an increase in internal pressure that can develop within the container as the contents are heated.
The retort process, while being an efficient heat treating or sterilizing process, can be harsh on container components because of the temperature and pressure variations which the container components are subjected to. Materials that are commonly used for reclosable containers such as plastic bottles can soften and distort during retort processing. Materials utilized for liners or seals can soften and lose sealability. As liner materials are generally separate components when compared to the container and closure, differences in materials can cause small gaps or pinholes to form at an interface of the components. Unwanted venting would allow products to escape the container as the pressure increases during the retort process and can allow process bath water when utilized to enter the container when internal pressure decreases relative to the external pressure and the container returns to an ambient condition.
Additional considerations are present when the container includes a threaded closure and a retort liner present between the closure and container body. An adequate seal must be maintained between the liner and container body, as well as the liner and the closure, and closure with the container body. These contact points can increase the number of possible manufacturing errors that can allow for product contamination.
The use of retort liners in sealing a container requires a liner that can withstand the retort process without failing, maintain a suitable oxygen barrier for a desired lifespan of the product and also be easily removable from the container when desired by a consumer. Some liners may adhere so tightly to a lip of the container that when the consumer attempts to remove a closure which contains a liner, a liner can tear into small pieces or can leave fragments along the container rim. Thereafter, the product may settle undesirably under the liner fragments, especially when the product is a beverage. Torn or broken liners can increase the probability of contamination of the product.
United Kingdom Patent No. 1,196,125 relates to sealing gaskets for container closures, e.g., of the crown, roll-on thread, pre-threaded screw and lug types, and to their formation.
U.S. Pat. No. 4,807,772 relates to a polypropylene compression molded closure with an elastomer liner that is removable, the elastomer being a blend of polyethylene and a rubbery copolymer, containing oil.
U.S. Pat. No. 6,702,133 relates to a retortable all-plastic closure having a generally circular top portion and a generally cylindrical downwardly depending skirt.
U.S. Pat. No. 7,055,713 relates to a retortable container and closure for hermetic sealing of an open end thereof. The closure includes a metal end ring adapted to be double seamed to an open end of the retortable container, an intermediate area extending radially inward and defining an opening to an interior of the container, and a folded area folded into the interior of the container. The folded area extends radially outward from the opening and substantially parallel to at least an adjacent portion of the intermediate area. A first membrane patch overlaps and is bonded to an under side of the intermediate area of the end ring such that the first membrane patch prevents contamination of contents of the container by the metal end. A second membrane patch covers the opening and is bonded to an upper side of the first membrane patch.
U.S. Pat. No. 7,056,971 relates to a thermoplastic elastomer sealant which is oxygen-permeable and reportedly provided with barrier properties against oxygen by melt-blending with a liquid polyisobutene oil plasticizer in an amount insufficient to render the plasticized elastomer tacky. If made tacky, enough detackifier is reportedly used to allow the product to be formed into a removable seal. The TPE may be a conventional thermoplastic vulcanizate or a block copolymer of a vinyl aromatic compound, typically styrene, and a conjugated diene, typically butadiene or isoprene, or mixtures thereof; the block may be a diblock, triblock or higher block, but the preferred polyblock copolymer is a triblock with styrene end-blocks and a butadiene/isoprene mid-block. Preferably the diene mid-block is hydrogenated to provide a poly(lower)-monoolefin mid-block. When the TPE is a TPV, some or all of the mineral oil used to make the TPV processable may also be substituted with the polyisobutene plasticizer. The elastomeric product is reportedly useful for sealing elements for containers in which foods, beverages and medical products must be preserved for a long period.
U.S. Patent Application Publication No. 2003/0116524 relates to a closure which reportedly provides a means for maintaining an effective pressure against a peelable seal affixed to a container lip as the sealed container is exposed to relatively high temperature and pressure conditions. The closure includes a liner which abuts a surface of the seal so as to sandwich the seal between the liner and the container lip. The liner defines a resting thickness at ambient temperature and pressure conditions and is made from a material reportedly capable of being compressed to a thickness less than the resting thickness and of recovering to a recovery thickness sufficient to allow the liner to maintain a positive pressure against the seal upon exposure to elevated temperatures, elevated pressure, or a combination of elevated temperature and elevated pressure.
U.S. Patent Application Publication No. 2006/0286327 relates to retort food containers comprising polyester compositions comprising polyesters which comprise a dicarboxylic acid component having terephthalic acid residues; optionally, aromatic dicarboxylic acid residues or aliphatic dicarboxylic acid residues or ester residues thereof; 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues; and 1,4-cyclohexane-dimethanol residues.
European Patent Publication No. 0 380 269 relates to a method of treating a food container having a plastic body portion and a lid sealed thereto for the purpose of reportedly insuring that micro-organisms cannot penetrate into the interior of the container through any faults or imperfections in the seal between the lid and the body portion, which method comprises forming a polymeric coating layer over the external surface of the container in such a manner as to encompass completely the join between the lid and the body of the container, the resultant polymeric coating layer being a retortable polymer.
European Patent Publication No. 0 659 655 relates to a plastic closure for sealing containers which has been filled with contents that are hot or which are to be retorted. The closure is made of thermosetting or thermoplastic material. The closure includes a base wall and a peripheral skirt. The skirt is formed for engaging a container. The base wall of the closure having an inner surface with a liner thereon. A reaction hot melt adhesive bonds the liner to the inner surface. The reactive hot melt adhesive is cross-linkable such that after the liner is applied and the adhesive cures, the adhesive bonds the liner to the inner surface of the base wall of the closure such that the liner will reportedly withstand and resist deformation under vacuum caused by cooling of the hot contents in a container or caused by retorting the contents of a container and subsequent cooling. The reactive hot melt adhesive may be a cross-linkable adhesive selected from the group consisting of polyurethane and silicone. The liner being adhered may be made of ethylene, polypropylene, α-olefin copolymers, i.e., ethylene-octane, propylene-ethylene or butylene-ethylene and SBR rubber.
European Patent Publication No. 1 845 027 involves the use of plasticized PVC compounds to meet the difficult requirements relating to twist-off cap closures. Replacement of PVC compounds in the closure would reportedly enable the industry to take advantageous use of twist-off cap closures that do not have the drawbacks generated by the use of PVC. Further, this application relates to compositions for hermetic closures for receptacles and also to hermetic closures for carbonated-drink receptacles, which comprise the above compositions and which are designed so that their cap can easily be twisted off.
Japanese Publication No. 11-180457 relates to providing a cap with a sterilized filling liner which reportedly makes cap opening torque small in opening the cap while keeping a big cap fitting angle in closing the cap.
Japanese Publication No. 2004-224975 provides a composition for a cap liner material reportedly having excellent sealability, cap-openability, sanitariness and moldability and keeping good sealability and cap-openability even after the heat-treatment at a high temperature, and thus reportedly useful as a cap liner and a cap of various food containers and drink containers necessitating high-temperature sterilization such as retort treatment.